1. Any mathematical expression in which an addition operator is applied to two or more subexpressions each of which is an application of a multiplication operator. The most common case would be scalar addition and multiplication, e.g. ab + cd but the term is used for other kinds of operators with similar properties, such as AND and OR in Boolean algebra, e.g. (a AND b) OR (c AND d) 2. algebraic data type. (2008-02-04)